Modern computer systems generate large amounts of data. For example, events within a telecommunications infrastructure or a data-center may result in multiple real-time data streams. Event processing is a field of technology directed towards analyzing these data streams. For example, the result of this analysis may be used to manage network services and/or to control complex computer systems. Often the result of event processing is used to control technical systems in real-time or near real-time. One challenge in implementing event processing systems is to handle large numbers of data items that accrue in short time periods. For example, events may occur asynchronously and at different frequencies within a given time period. Another challenge is to perform complex processing operations while still retaining the ability to control technical systems in real-time or near real-time. For example, detecting and/or predicting security breaches on a computer or telecommunications network may involve the processing of multiple asynchronous data sources in real-time in order to prevent significant damage and/or data loss.